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Annegret Meermeier, Markus Lappe, Michele Rucci; Mapping visibility around the blind spot. Journal of Vision 2018;18(10):1279. doi: 10.1167/18.10.1279.
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The natural blind spot, the retinal scotoma at ~15° eccentricity, is a necessary nuisance for the visual system, as it corresponds to the location where nerve fibers and blood vessels go through the retina. Although the anatomy of the blind spot is well characterized, little is known about visual functions at the edges of the blind spot and how signals in this region affect perceptual filling in within the blind spot itself. A fundamental challenge to this end is the incessant presence of eye movements in the human eye, which, in standard experimental procedures, smear visibility maps around the blind spot. To circumvent these problems, here we combined several experimental techniques and mapped the blind spot borders of the human right eye along the horizontal meridian. The eye movements of 5 observers were recorded at high-resolution using a newly developed digital Dual Purkinje eye-tracker, a system with sub-arcminute resolution. A specially-designed calibration procedure enabled accurate positioning of a visual probe (a 2x2 arcmin high-contrast dot displayed for 14 ms) relative to the line of sight. The probe was maintained at a fixed location on the retina by means of retinal stabilization, a procedure that continually updates the position of the stimulus on the monitor to compensate for the observer's eye movements. In a 2AFC task, subjects reported detection of the probe via button press. We determined the detection rate as a function of visual eccentricity. We show that the transition zone from full visibility to total invisibility around the blind spot covers approximately 30'. On average, at the nasal side, visibility dropped from 75% to 25% in approximately 11'. At the temporal side visibility increased from 25% to 75% in approximately 17'. These results show the existence of intermediate visibility zones surrounding the blind spot.
Meeting abstract presented at VSS 2018
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